Pointer identification has a number of advantages in a touch system such as being able to attribute different colours to each particular pointer. In more advanced systems, the pointer may be attributed to a particular user. Prior methods of determining a pointer type have been disclosed in U.S. Pat. Nos. 6,954,197; 7,532,206; 7,619,617; 8,228,304; 8,537,134; and 8,872,772 as well as U.S. Publication No. 2009/0278794; all to SMART Technologies, ULC assignee of the present invention, all of which are herein incorporated by reference in their entirety.
U.S. Pat. No. 6,954,197 describes a camera-based touch system wherein two cameras acquire images of the touch surface from different locations and having overlapping fields of view. A digital signal processor is associated with each camera. The digital signal processors process pixel data to generate pointer characteristic data to identify the edges of the pointer. A master processor triangulates the edge information in the pointer characteristic data to determine a bounding area that represents a pointer perimeter.
U.S. Pat. No. 7,532,206 describes a camera-based touch system comprises a touch surface and at least one imaging device acquiring images of the touch surface. At least one processor analyzes images acquired by the one imaging device to determine the type of pointer used to contact said touch surface and the touch location on touch surface. The pointer type is determined by at least one three-dimensional formation adjacent the end of the pointer.
U.S. Pat. No. 8,872,772 describes a machine vision interactive input system detecting a pointer placed within the field of view of an imaging assembly. The pointer having at least one retro-reflective band placed thereon. The pointer type is identified by the at least one retro-reflective band within the images.
U.S. Publication No. 2009/0278794 describes an interactive input system having one or more imaging devices capturing images of a region of interest. A plurality of radiation sources such as located on each pointer are modulated whereby the processed images permit identification of the pointer based on the modulated radiation.
Prior methods have relied on sophisticated image sensors, additional hardware components, and/or limited touch area size. Although these prior methods work well, there is a need for a less expensive but reliable alternative for pointer identification on large format touch screens. Prior methods have compensated for inexpensive image sensors by adding extra cameras, making the pointer active (e.g. emitting LED light), increasing the focal length of the camera's lens, etc. These systems tend to have more complexity than may be necessary.
The invention described herein at least provides improved pointer recognition on large format touch screens utilizing image sensors with limited touch screen area size.